Heretofore, as disclosed and claimed in U.S. Pat. No. 2,916,163, granted Dec. 8, 1959 to David S. Campbell, there has been constructed a high capacity draft gear, which, generally speaking, utilizes in a housing a friction cushioning element in tandem with a coil spring cushioning element and longer gear travel is accommodated with a conventional type of coil spring cushioning element by utilizing a guide stem that is movable with the follower for the coil spring element to cooperate with the spring element and give it necessary columnar stability during compression. During release, the coil spring aligns the guide stem, which cooperates with an intermediate follower for preventing tipping of this follower, thereby avoiding binding or sticking of the gear. Additional capacity is achieved through longer travel and through the use of corner coil springs mounted in individual spring chambers that extend parallel to the main coil spring chamber. The action of the friction system throughout the gear closure absorbs sufficient energy to maintain reaction pressures on the car within required limits.
As is well known, draft gears are subjected to two major types of loading, namely buff and draft. The buff loading occurs during train make up, train operations, train braking, and "in train action" to compensate for relative motion between railroad cars. This type of loading manifests itself in a coupler shank compressive force which is transmitted to the follower block which, in turn, distributes the loading among the center wedge and two movable plates in the draft gear. This force is transmitted through the friction clutch mechanism and is borne by the housing walls which are supported by the rear lugs of the draft gear pocket in the car.
On the other hand, draft loading occurs during locomotive tractive actions as well as "in train action" to compensate for relative motion between railroad cars. This type of loading manifests itself in a coupler shank tensile force which is transmitted through the coupler key and yoke to the draft gear housing end. This force is transmitted from the housing end through the housing walls, friction clutch mechanism, and follower block which is supported by the front lugs of the draft gear pocket of the car.
In the draft gear design of the aforementioned U.S. Pat. No. 2,916,163, the yoke bears against the center-section of the draft gear end where the load is distributed outward to the walls of the housing. Because of the rigid connection between the bottom portion of the housing and the walls, a bending moment is transmitted into the side walls causing them to flex.
Service conditions existing at the time the aforementioned draft gear design was constructed and placed into service involved applications to 70-ton rail cars with relatively low utilization and shorter train lengths. Consequently, a reasonable number of years of service could be expected from the draft gear. Subsequently, with the introduction of unit trains, increased car capacity and utilization, and longer train lengths have all contributed to increased magnitude and number of draftbuff fatigue cycles on the draft gear. Even today in normal rail car service, the aforementioned draft gear design is satisfactory and provides a reasonable life.
Under severe service conditions, however, the housing side wall flexure is increased which reduces the fatigue life of the draft gear.
Accordingly, the object of the present invention is to increase the fatigue life of the draft gear housing.
Another object of the invention is to strengthen the draft gear housing against a side wall flexing face imposed by the yoke under draft bearing against the housing end.
Yet another object is to increase the rigidity of the housing side walls by increasing the cross-sectional areas of the main spring guide ribs to better support the housing end against draft force induced by the yoke.